JP2002233156A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power converter fitted with a means which performs superior detection of the reduction of a source voltage, even when a power source is influenced by seasonal variations or operating conditions of a large- capacity load connected to the same system, without being influenced by these. SOLUTION: An AC source voltage signal Vac which is an instantaneous value of an AC power source 1, detected by a source voltage detector composed of a transformer 5, a rectifier 6, and an analog-to-digital converter 7, is average by an averaging circuit 9, and an average AC source voltage signal Vave is outputted. The average signal Vave and the signal Vac are compared, and its deviation is compared with a fixed value (Vpsf) by a comparator 8. When the deviation is equal to or larger than the fixed value, a detection signal PSF-S of a source voltage reduction is outputted. Consequently, misdetection of source voltage lowering caused by an influence of variations on the power supply is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion device, and more particularly to a power conversion device capable of detecting occurrence of a power supply voltage drop with high sensitivity without erroneous detection and maintaining stable control. It is.

[0002]

2. Description of the Related Art FIG. 6 shows a configuration of a thyristor leonard device provided with a power supply drop detection circuit.

In FIG. 6, an AC power supply 1 includes a forward converter for converting AC power from the AC power supply 1 into an arbitrary DC voltage, and a regenerative power from a DC motor 3 serving as a load. A thyristor converter 2 composed of an inverter for regenerating the thyristor 1 is connected.

If the thyristor converter 2 performs a regenerative operation and a voltage drop or a power failure of the AC power supply 1 occurs, the commutation may fail and a short circuit may occur. Is provided with a power supply voltage drop detection circuit 4 for detecting that the voltage of the power supply has dropped and executing a predetermined protection operation.

[0005] The power supply voltage drop detection circuit 4 includes an AC power supply voltage signal Vac detected by a power supply voltage signal detection circuit including a transformer 5, a rectifier 6, and an A / D converter 7 from one AC power supply system, By inputting the voltage detection signal Vpsf to the comparator 8, the power supply voltage drop detection signal PSF
_S is output.

When the power supply voltage drop detection signal PSF_S operates, the thyristor leonard device performs a predetermined protection operation.

[0007]

However, the conventional power supply voltage drop detection circuit 4 as described above has the following problems.

[0008] One AC power supply system fluctuates under the influence of the season and the operating condition of a large-capacity load connected to the same system.

The fluctuation of the AC power supply 1 affects the power supply voltage drop detection circuit 4 as follows.

For example, when the load of a large-capacity load of the same system increases and the voltage of one AC power supply decreases, the difference between the power supply voltage detection signal Vpsf and the AC power supply voltage signal Vac decreases, and there is no room for power supply voltage detection. If the setting of the power supply voltage detection signal Vpsf is increased in order to increase the detection sensitivity, there is a possibility that an erroneous detection may occur.

For example, the power supply voltage drop detection signal PSF_S when the detection level is 85% is indicated by A in FIG. 7. As shown in FIG. 7, the occurrence of a power failure can be detected. If the voltage of the power supply drops by 15% or more, erroneous detection will occur even if no power failure occurs.

Further, when the load of the large-capacity load decreases and the voltage of one AC power supply increases, the AC power supply voltage signal Vac also increases, so that it is impossible to detect a decrease in the power supply voltage at the original detection level.

In view of the above, the present invention has been made in view of such a conventional point, and even when the power supply is affected by seasonal fluctuations or the operating condition of a large capacity load connected to the same system, It is an object of the present invention to provide a power conversion device provided with a unit capable of detecting a favorable power supply voltage drop without being affected by the above.

[0014]

According to a first aspect of the present invention, there is provided a power converter for converting power from a power supply into an arbitrary voltage, wherein the average power supply voltage is obtained by averaging a power supply voltage signal. Averaging means for obtaining a signal, and comparing the average power supply voltage signal obtained by the averaging means with the instantaneous value of the power supply voltage signal, and detecting a drop in the power supply voltage when the deviation exceeds a certain value. And a power supply voltage drop detecting means for outputting a power supply voltage drop detection signal.

According to the first aspect of the present invention, it is possible to prevent erroneous detection of a power supply voltage drop due to the influence of power supply fluctuations such as seasonal fluctuations.

According to a second aspect of the present invention, there is provided a power conversion apparatus for converting power from a power supply into an arbitrary voltage, wherein the averaging means obtains an average power supply voltage signal by averaging the power supply voltage signal. Short-time averaging means for obtaining a short-time average power supply voltage signal by averaging the power supply voltage signal in a short time with respect to the average power supply voltage signal obtained by the averaging means; The power supply voltage signal is compared with the short-time average power supply voltage signal obtained by the short-time averaging means, and when the deviation exceeds a certain value, the power supply voltage drop is detected. And a power-supply-voltage-drop detecting means for outputting

According to the second aspect of the present invention, it is possible to perform a power supply voltage drop detecting operation with less possibility of erroneous detection due to the influence of the power supply fluctuation than the first aspect of the present invention.

According to a third aspect of the present invention, in the power converter according to the first or second aspect, the power supply voltage drop detecting means includes a voltage drop rate detecting means for detecting a power supply voltage drop rate. When detecting a drop in the power supply voltage due to the deviation exceeding a certain value, only when the drop rate detected by the voltage drop rate detecting means is equal to or more than the set value,
It is characterized by outputting a power supply voltage drop detection signal.

According to the third aspect of the present invention, the power supply voltage drop detection operation is performed only when it is determined that the power supply voltage drop is abrupt. It is possible to prevent erroneous detection of the power supply voltage drop due to the drop.

According to a fourth aspect of the present invention, in the power converter according to the first or second aspect, the power supply voltage drop detecting means detects an increase in the load of a large capacity load connected to the same power supply system. A load increase detecting means for detecting the power supply voltage, and detecting a decrease in the power supply voltage due to a deviation exceeding a certain value. It is characterized in that the output of the voltage drop detection signal is limited.

According to the present invention, erroneous detection of a power supply voltage drop due to a voltage drop caused by an increase in the load of a large-capacity load connected to the same power supply system can be prevented.

According to a fifth aspect of the present invention, in the power converter according to the first or second aspect, the power supply voltage drop detecting means reduces the power supply voltage when the deviation becomes equal to or more than a certain value. Holding means for holding that the power supply voltage has been detected, and an instantaneous value, an average power supply voltage signal, or a short-time average power supply voltage signal of the power supply voltage signal when a decrease in the power supply voltage is detected because the deviation has become a certain value or more. Memory means for storing, and when the instantaneous value of the power supply voltage signal or short-time average power supply voltage signal returns to a value equal to or greater than the memory value of the memory means or a value obtained by adding a bias amount to the memory value, detection of a power supply voltage drop by the holding means. And reset means for resetting the holding of the data.

According to the present invention, when the power supply voltage returns from the low state to a predetermined value or more, the held power supply voltage detection can be recovered.

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following drawings, the same reference numerals indicate the same parts or corresponding parts including the figures showing the conventional example.

(First Embodiment) A power converter according to a first embodiment of the present invention will be described with reference to FIG.

In FIG. 1, an AC power supply voltage signal Vac which is an instantaneous value of the AC power supply 1 detected by a power supply voltage detection circuit including a transformer 5, a rectifier 6, and an A / D converter 7
Are input to the averaging circuit 9, and the averaging circuit 9 outputs an average AC power supply voltage signal Vave.

The average AC power supply voltage signal Vave is compared with an AC power supply voltage signal Vac, which is an instantaneous value of the AC power supply 1, and the deviation thereof and the power supply voltage detection signal Vpsf are input to a comparator 8, whereby Power supply voltage drop detection signal PS
F_S is output.

For example, if the detection level is 85% of the average AC power supply voltage signal Vave, the deviation between the average AC power supply voltage signal Vave and the AC power supply voltage signal Vac is 15% or more of the average AC power supply voltage signal Vave. If it becomes
Power supply voltage drop detection signal PSF_S is output (comparator 8
The output signal changes from “1” to “0”), and a drop in the AC power supply voltage can be detected.

In this case, the power supply voltage drop detection signal PSF_
S is indicated by B in FIG. 7. As shown in FIG. 7, the detection point in this embodiment is to detect at 85% of the average AC power supply voltage signal Vave,
When a power failure occurs, the AC power supply voltage signal Vac, which is an instantaneous value of one AC power supply, is 15
If the AC power supply voltage signal Vac, which is the instantaneous value of the AC power supply 1, is reduced by 15% or more due to power supply fluctuation, this is detected as in the case of the conventional example shown by A in FIG. This does not cause erroneous detection.

(Second Embodiment) Next, a power converter according to a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, a short-time averaging circuit 10 is added to the configuration of the first embodiment shown in FIG.

Referring to FIG. 2, an AC power supply voltage signal Vac of the AC power supply 1 detected by a power supply voltage detection circuit including a transformer 5, a rectifier 6, and an A / D converter 7 is input to an averaging circuit 9 and averaged. The average AC power supply voltage signal Vave is output from the conversion circuit 9.

The average AC power supply voltage signal Vave and the short-time average AC power supply voltage signal averaged by the short-time averaging circuit 10 for averaging the AC power supply 1 with respect to the averaging circuit 9 in a sufficiently short time. Compared with Vave1, the deviation and the power supply voltage detection signal Vpsf are input to the comparator 8, so that the power supply voltage drop detection signal PSF_S is output.

That is, when the deviation between the average AC power supply voltage signal Vave and the short-time average AC power supply voltage signal Vave1 becomes equal to or greater than a predetermined value, the power supply voltage drop detection signal PSF_
S is output (the output signal of the comparator 8 changes from “1” to “0”), and a drop in the AC power supply voltage can be detected.

According to this embodiment, a power supply voltage drop detection operation in which the possibility of erroneous detection due to the influence of power supply fluctuation is further reduced than in the first embodiment.

(Third Embodiment) Next, a power converter according to a third embodiment of the present invention will be described. This third embodiment has the same configuration as the first or second embodiment,
A voltage drop rate detector and an OR circuit are added, and the drop of the AC power supply voltage is detected in addition to the condition that the drop of the AC power supply voltage is determined to be rapid.
FIG. 3 shows an example in which a voltage drop rate detector 11 and an OR circuit 20 are added to the configuration of the second embodiment shown in FIG.

In FIG. 3, an AC power supply voltage signal Vac, which is an instantaneous value of the AC power supply 1 detected by a voltage detection circuit including a transformer 5, a rectifier 6, and an A / D converter 7, is a voltage drop rate detector 11 The power supply voltage change rate signal dv / dt is output when the AC power supply voltage signal Vac decreases at a reduction rate equal to or higher than the set value.

The power supply voltage change rate signal dv / dt is added to the output condition of the power supply voltage drop detection signal PSF_S, and the power supply voltage drop detection is executed only when it is determined that the power supply voltage drop is sharp. .

That is, when the power supply voltage drop detection signal PSF_S is output from the comparator 8 (the output signal of the comparator 8 becomes “0”) and the power supply voltage change rate signal dv / dt is output (the voltage drop rate detection The power supply voltage drop detection signal PSF_S is output from the OR circuit 20 only when the output signal of the OR circuit 20 becomes “0” (the output of the OR circuit 20 is “0”).
Therefore, the power supply voltage drop detection is executed only when it is determined that the power supply voltage drop is sharp.

As described above, the detection of the power supply voltage drop is executed only when it is determined that the power supply voltage drop is abrupt, thereby erroneously detecting the power supply voltage drop due to the gradual voltage drop due to the load fluctuation of the AC power supply system. Can be prevented.

The voltage drop rate detector 11 and the OR circuit 20 can be added to the configuration of the first embodiment shown in FIG.

(Fourth Embodiment) Next, a power converter according to a fourth embodiment of the present invention will be described. This fourth embodiment has the same configuration as the first or second embodiment,
An A / D converter, a comparator, and an OR circuit are added to monitor a large-capacity load connected to the same AC power supply system and limit detection of a drop in AC power supply voltage that occurs when the large-capacity load increases. This is to add a condition. FIG.
Shows an example in which an A / D converter 17, a comparator 18, and an OR circuit 20 are added to the configuration of the second embodiment shown in FIG.

In FIG. 4, a load signal P from a large-capacity load 12 connected to the same AC power supply system as the AC power supply 1 is shown.
By inputting OWER (kW) and the system load increase reference P_REF to the comparator 8, the system load increase signal P_IN
C is output. When the system load increase signal P_INC is added to the output condition of the power supply voltage drop detection signal PSF_S, and it is determined that the decrease in the power supply voltage is due to an increase in the load of the large capacity load 12 connected to the same AC power supply system, Execution of the power supply voltage drop detection is restricted.

That is, the output signal of the large capacity load 12 is A / D
The signal is supplied to the comparator 18 via the converter 17 as the load amount signal POWER (kW), and the system load increase reference P_RE
Compared to F. When the load amount signal POWER (kW) becomes equal to or more than the system load increase reference P_REF, the system load increase signal P_INC is output (the output signal of the comparator 18 becomes “1”). Power supply voltage drop detection signal P from comparator 8
When SF_S is output (comparator 8 output signal is
Even if it becomes “0”), the system load increase signal P_IN
When C is output (when the output signal of the comparator 18 is “1”), the power supply voltage drop detection signal PS is output from the OR circuit 20.
F_S is not output (the output signal of the OR circuit 20 does not become “0”), and the execution of the power supply voltage drop detection is restricted.

As described above, when it is determined that the load of the large-capacity load 12 connected to the same AC power supply system is increased by a predetermined amount or more, the detection of the power supply voltage drop is limited, so that the load of the large-capacity load 12 is reduced. It is possible to prevent erroneous detection of a power supply voltage drop due to a voltage drop of the AC power supply 1 caused by the increase.

The A / D converter 17, the comparator 18, and the OR circuit 20 are added to the configuration of the first embodiment shown in FIG.
And can be implemented similarly.

(Fifth Embodiment) Next, a power converter according to a fifth embodiment of the present invention will be described. This fifth embodiment has the configuration of the first or second embodiment,
A power supply drop detection voltage memory, a single shot, a holding circuit, and a comparison circuit are added, and when a power supply voltage drop is detected, the instantaneous value of the AC power supply voltage signal, or the average power supply voltage signal obtained by averaging the AC power supply voltage signal, or the average Stores the short-term average AC power supply voltage signal averaged in a short time that is sufficiently short for the power supply voltage, and is averaged sufficiently shortly for the instantaneous value or average power supply voltage of the AC power supply voltage signal. When the detected signal returns to the memory value or more or the value obtained by adding the bias amount to the memory value, the held power supply voltage drop detection is reset. FIG. 5 shows a power supply voltage drop detection in an example in which a power supply drop detection voltage memory 13, a single shot 14, a holding circuit 15, and a comparison circuit 19 are added to the configuration of the first embodiment shown in FIG. 2 shows a configuration of a circuit 4 part.

In FIG. 5, as means for restoring the power supply voltage drop detection signal PSF_S, which is an output signal of the holding circuit 15 holding the output signal from the comparator 8, an AC power supply voltage signal Vac at the time of power supply voltage drop detection or An average power supply voltage signal Vave obtained by averaging the AC power supply voltage signal at the time of the detection of the power supply voltage drop (FIG.
3, the power supply voltage drop detection voltage signal Vmem stored in
The power supply voltage drop detection reset signal PSF_RST obtained by inputting the AC power supply voltage signal Vac, which is the instantaneous value of the AC power supply 1, to the comparator 19 is used.

That is, the AC power supply voltage signal Va when the power supply voltage drop is detected (when the output signal of the comparator 8 becomes “0”)
c is the voltage Vme when the power supply voltage drop is detected by the memory circuit 13.
stored as m. Then, the AC power supply voltage signal Vac, which is the instantaneous value of the AC power supply 1, is input to the comparator 19, and the comparator 19 detects the AC power supply voltage signal Vac and the power supply voltage drop detection voltage signal Vmem or the power supply voltage drop detection. And a value obtained by adding the bias amount BIAS to the hour voltage signal Vmem.
em is added to the value obtained by adding the bias amount BIAS), and the bias amount BIAS is added to the AC power supply voltage signal Vac when the power supply voltage drop is detected or the voltage signal Vmem when the power supply voltage drop is detected. When the value becomes equal to or greater than the set value, the power supply voltage drop detection reset signal PSF_RST is output (the output signal of the comparator 19 becomes “0”). This power supply voltage drop detection reset signal P
SF_RST is a reset pulse signal of the holding circuit 15 via the single shot 14 as a reset pulse signal.
To restore the power supply voltage drop detection signal PSF_S held by the holding circuit 15.

In this manner, when the AC power supply voltage signal Vac, which is the instantaneous value of the AC power supply 1, returns from the lowered state to a predetermined value or more, the held power supply voltage drop detection can be recovered.

The power supply drop detection voltage memory 13, the single shot 14, the holding circuit 15, and the comparison circuit 19 can be added to the configuration of the second embodiment shown in FIG.

[0051]

As described above, according to the present invention, even when the power supply is affected by seasonal fluctuations or the operating condition of a large-capacity load connected to the same system, the power supply is not affected by those fluctuations. It is possible to provide a power converter capable of detecting a favorable power supply voltage drop and maintaining stable control.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a power conversion device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a power conversion device according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a power conversion device according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a power converter according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a main part of a power conversion device according to a fifth embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional example.

FIG. 7 is a timing chart for comparing and explaining a power supply voltage drop detection operation of the conventional example and the first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... AC power supply 2 ... Thyristor converter 3 ... DC motor 4 ... Power supply voltage drop detection circuit 5 ... Transformer 6 ... Rectifier 7, 17 ... A / D converter 8, 18, 19 ... Comparator 9 ... Averaging circuit 10 ... Short-time averaging circuit 11 ... Voltage drop rate detector 12 ... Large load 13 ... Power supply drop detection voltage memory 14 ... Single shot 15 ... Holding circuit 20 ... OR circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tadamitsu Yoshikawa 1 Toshiba-cho, Fuchu-shi, Tokyo F-term in Fuchu Works, Toshiba Corporation (reference) 5H006 AA04 BB05 CA03 CC01 DB07 DC05 5H740 AA08 BA01 BB07 BB10 MM01

Claims (5)

[Claims] 1. A power conversion device for converting power from a power supply into an arbitrary voltage, an averaging means for obtaining an average power supply voltage signal obtained by averaging the power supply voltage signal, and the average power supply obtained by the averaging means. A power supply voltage drop detecting means for comparing a voltage signal with an instantaneous value of the power supply voltage signal, detecting a drop in the power supply voltage when the deviation becomes a certain value or more, and outputting a power supply voltage drop detection signal; A power conversion device comprising: 2. A power conversion device for converting power from a power supply into an arbitrary voltage, an averaging means for obtaining an average power supply voltage signal by averaging a power supply voltage signal, and the average power supply obtained by the averaging means. A short-time averaging means for obtaining a short-time average power supply voltage signal obtained by averaging the power supply voltage signal in a short time with respect to a voltage signal; and the average power supply voltage signal obtained by the averaging means and the short-time averaging. Means for detecting a drop in the power supply voltage when the deviation has become equal to or greater than a certain value, and outputting a power supply voltage drop detection signal. And a power conversion device. 3. The power supply voltage drop detecting means includes a voltage drop rate detecting means for detecting a power supply voltage drop rate, and when the power supply voltage drop is detected when the deviation becomes equal to or more than a certain value, The power supply according to claim 1 or 2, wherein the power supply voltage drop detection signal is output only when the voltage drop rate detected by the voltage drop rate detection unit is equal to or greater than a set value. Conversion device. 4. The power supply voltage drop detecting means includes a load increase detecting means for detecting an increase in the load of a large capacity load connected to the same power supply system. Even if a voltage drop is detected, the output of the power supply voltage drop detection signal is limited when the load increase by a predetermined amount or more is detected by the load increase detection means. The power converter according to claim 1 or 2. 5. A power supply voltage drop detecting means for holding a detection that a power supply voltage drop has been detected when said deviation has become equal to or greater than a certain value, and said power supply voltage drop detecting means having provided that said deviation has become equal to or greater than a certain value. A memory means for storing an instantaneous value of the power supply voltage signal or the average power supply voltage signal or the short-time average power supply voltage signal when a decrease in the power supply voltage is detected; Reset means for resetting the holding of the power supply voltage drop detection by the holding means when the average power supply voltage signal returns to a value equal to or more than the memory value of the memory means or a value obtained by adding a bias amount to the memory value. The power converter according to claim 1, wherein the power converter is provided.